(1) Theoretical and Historical StudyHistory of school class system in Japan was described focusing on the establishment of class system in Meiji era, the effort to reduce class size in Taisho liberal education movement, and the recent expansion of team teaching and teacher employment by local government. The history and logic of class reorganization was also clarified through historical and empirical studies.(2) Effectiveness StudyEmpirical studies were made through questionnaires to principals, head teachers and teachers of kindergartens, primary schools and junior high schools, and to the 5ィイD1thィエD1 year pupils in primary schools and 2ィイD1ndィエD1 year students in junior high schools. Through these studies we clarified the effect of class size to teaching and learning activities, and opinions about the proper size of class and the system of school personnel assignment.(3) Policy StudyThe local government policies concerning class organization and teacher assignment were clarified through questionnaires to education boards. Some case studies were made about the effect of the increase and decrease of the number of classes to educational activities. And the historical change of the law about the standards of class size and the number of school personnel in senior high schools was studied to suggest the directions of the reform.(4) Comparative StudyWe made research on the standards about the class size and the number of teachers and other staffs in schools in many countries and about the policies concerning these matters in the USA, Germany, England, France and Russia.(5) ConclusionsBased on the studies above we suggested some principles for the reform of the system of class organization and school personnel assignment.